Normal paraffins have a multitude of uses, both as end products and as reactants for downstream processes. Carbon chain length of the normal paraffins varies depending upon an intended end use, with carbon chain length controlling various properties of the normal paraffins. For example, normal paraffins range from methane, which is in the gaseous phase under atmospheric and ambient conditions, to solid wax forms (such as C20 to C40 paraffins), as well as forms having even higher carbon chain lengths. Normal paraffins are also useful components within various forms of fuel, with different normal paraffins present in different types of fuel. For example, diesel fuel generally has C9 to C22 paraffins, and many diesel fuels have high amounts of C17 and C18 normal paraffins. On the other hand, jet fuel generally has a content of C9 to C16 normal paraffins, with a content of C17 and C18 normal paraffins desirably minimized in the jet fuel.
Methods of preparing normal paraffins from an unsaturated feed are generally known in the art. Normal paraffins occur naturally, in petroleum deposits among other sources, and various techniques exist for separating the normal paraffins from other compounds in the naturally-occurring sources. Normal paraffins can also be prepared through various techniques by which hydrocarbons or other carbon-containing compounds are processed to saturate olefin bonds and/or remove heterogeneous atoms (such as oxygen, nitrogen, sulfur, or other elements that are commonly present in carbon-containing compounds). With a desire to obtain hydrocarbons from renewable sources, such as vegetable and animal oils, techniques for preparing normal paraffins from naturally-occurring triglycerides and free fatty acids have become a focus in industry. One example of an existing technique involves hydrogenation of carbon-carbon double bonds in the vegetable and animal oils and deoxygenation in the presence of additional hydrogen and a deoxygenation catalyst to produce normal paraffins. Such techniques enable deoxygenation of compounds in the vegetable and animal oils to produce normal paraffins and other hydrocarbons. However, the hydrogenation/deoxygenation processes generally yield normal paraffins that boil in the diesel range, depending upon the particular type of vegetable or animal oil. For example, hydrogenation/deoxygenation of soybean oil generally yields propane as well as C17 and C18 normal paraffins, and with smaller amounts of C15 and C16 normal paraffins also produced. For certain applications, such as for renewable jet fuel and for production of linear alkyl benzene, there is a desire to obtain a hydrocarbon stream that primarily includes C9 to C15 normal paraffins. To convert the C17 and C18 normal paraffins into paraffins in the C9 to C15 paraffins range, an additional cracking process is generally required under severe conditions that promote both desired cracking/isomerization and undesired over-cracking reactions. Namely, while cracking serves to convert a portion of the C17 and C18 normal paraffins to C9 to C15 normal paraffins, low-octane naphtha (e.g., C4 to C8 normal paraffins) is also produced in appreciable quantities, thereby degrading the potential yield of the desired C9 to C15 normal paraffins.
Accordingly, it is desirable to provide novel methods of preparing normal paraffins, as well as methods of preparing hydrocarbon product streams from the normal paraffins and apparatuses for preparing the normal paraffins. There is also a desire to provide novel methods and apparatuses that enable appreciable amounts of C9 to C15 normal paraffins to be obtained from renewable feedstock, such as vegetable and animal oil, while avoiding severe cracking conditions that produce excessive amounts of C4 to C8 normal paraffins. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.